A deep ultraviolet LED with a light emission wavelength of less than or equal to 280 nm is attracting attention as an alternative technology for mercury germicidal lamps in a variety of fields of application, such as sterilization, water purification, air purification, and medical care. However, the wall-plug efficiency (WPE) of a LED is as low as several %, which is significantly lower than a wall-plug efficiency of 20% of a mercury lamp. This is mainly because greater than or equal to 50% of the emitted light is absorbed by a p-GaN contact layer, with the result that the light extraction efficiency (LEE) becomes as low as about 6%.
According to Patent Literature 1, photonic crystals are provided in the thickness direction in a region including an interface between a p-GaN contact layer and a p-AlGaN layer, so that incident light is reflected and the aforementioned absorption is suppressed.